Training the Core in the Sagittal Plane Part I: Anatomy and Function

The core…

What a popular buzzword.

If you’ve read any fitness related article on the Internet over the past 2-3 years you’ve probably heard it.

But what is the core?

What is it supposed to do?

How do you train it?

Where should you start?

Where should you go?

What exercises actually work and what exercises are just fluff (I’m talking to you six pack shortcut peeps)?

In this two part series we’re going to be talking about all the above and a little more with respect to the core and the sagittal plane. In particular, I’d like to outline and give you a game plan for how to appropriately tackle stage 1 of either your own or your athletes program.

And to be perfectly clear, when I say stage 1 I’m referring to the sagittal plane and being able to control flexion and extension. This is absolutely essential because if you can’t control the sagittal plane, then you will never be able to control the frontal and transverse planes as well.

Thus, this two part series you are embarking on is going to focus solely on the core and how it relates to controlling the sagittal plane (when you hear sagittal plane just think flexion and extension).

Unfortunately, we can’t have this conversation if we aren’t on the same page when it comes to anatomy, so Part I of this series (aka what you’re reading right now) will be devoted to talking about anatomy and the basic “job” of the core, while Part II will focus on the training and application side of things.

I know…anatomy isn’t sexy, can be a little wordy, and is often downright boring, but knowing it will make you a better athlete and coach. To help make this a little more interesting, and in hopes that you’ll actually read this, we’re going to be relating it all back to Batman because who doesn’t love Batman.

*side note: the Batman v. Superman move is coming out March 25th and should probably be on your calendar if it isn’t already.

Thus, let’s get started with what in the world the “core” is actually supposed to do.

What’s the Job of the Core

Understanding this concept is essential to tying together the rest of the 2 part series.

To quote Shirley Sahrmann:

“The most important aspect of abdominal muscle performance is obtaining the control that is necessary to (1) appropriately stabilize the spine, (2) maintain optimal alignment and movement relationships between the pelvis and the spine, and (3) prevent excessive stress and compensatory motions of the pelvis during movements of the extremities.”[i]

To summarize that and put it in plain English (and add a little flavor): the job of your core is to stabilize/maintain optimal position of your pelvis and ribs so that your arms and legs can function the way we want them to. And it does this by getting your ribs “down” (rib internal rotation) and your pelvis “underneath” you (posterior tilt is a popular word for this but there are things happening in all three planes of motion).

Let me clarify really quickly that you don’t want to take the “rib down” and “pelvis underneath you” cues too far. That can be just as bad. I’m merely making the assumption that you’re going to be patterned, that you’re going to have a rib flare, and that you’re going to have a pelvis that has a tendency to roll forward into anterior tilt because I haven’t seen a single person in over 2 years who doesn’t present this way. Thus, bringing your ribs back down and pelvis back underneath you is merely getting them where we want them to be. Then you have to learn to maintain it, but that’s more the focus of Part II.

Here’s a quick video to help put this into perspective for you (and it will also serve as a great lead in to Part II of this series where we focus on performance):

To review: the job of your core is to stabilize and maintain pelvic and thoracic position to allow your arms and legs to do what we want.

Some Anatomy

In order to adequately understand what we are trying to accomplish when we train “the core,” you’ve gotta know a little anatomy.

Of primary concern, for this article at least, are the following muscles:

  • -Rectus abdominis
  • -Internal obliques
  • -External obliques
  • -Transverse abdominis
  • -Lats
  • -Rectus femoris and TFL
  • -Serratus anterior

Let’s go ahead and address each of those accordingly

Rectus Abdominis (aka the six pack muscle)

*Couldn’t think of a good Batman reference for this. If you can, let me know.

rectus-abdominus.jpg

Who doesn’t love a good six-pack? As far as aesthetics go, it’s probably one of the most sought after traits and that’s totally fine. There’s absolutely nothing wrong with wanting to look like you just stepped out of a superhero movie.

When we’re talking about functionality and overall performance, however, the rectus abdominis equates to little more than a show muscle. And here’s why: it’s attachment sites suck when it comes to creating leverage.

As you can see in the above image, there’s a very tiny attachment site down on the pubic crest coupled with another small (and by small I’m talking surface area) attachment on both the xiphoid process and some costal cartilage.

In essence, this means the rectus abdominis has minimal capacity to truly impact the position of your pelvis and your ribs, which is of vital importance when you think back to what we need the core to do.

Internal Oblique, External Oblique, and Transverse Abdominis (aka Batman)

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Internal-Oblique.jpg
Transverse-Abdominus.jpg

Take a second and compare the images above to the image of the rectus abdominis. Notice any differences?

I sure hope you do. The internal oblique, external oblique and transverse abdominis are HUGE. Just look at the difference in attachment sites, and try and get an appreciation for how effective these three muscles are at controlling/impacting the position of your pelvis and your ribs (in turn giving your arms and legs a chance to work).

In other words, these three muscles are your Batman: here to fight evil and bring justice to your anatomical system.

Lats (aka Bane)

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Oh the lats. A much loved and sought after muscle by many, but like Bane they are very large and wield an incredible power (a power that was actually great enough to successfully break Batman’s back if you’re up on your Batman knowledge)

Let’s start with the pure size and magnitude of a single lat by looking at its attachment sites:

  • -Spinous processes of the lower six thoracic and all five lumbar vertebrae
  • -Posterior aspect of the ilium
  • -The lower three ribs
  • -Inferior angle of the scapula in some people
  • -Intertubercular groove on the anterior aspect of the humerus.

So yeah…this thing is big.

Now to the function as described by any anatomy textbook ever:

  • -Internally rotate the humerus
  • -Shoulder extension
  • -Shoulder adduction

That’s a nice list but it’s missing a MAJOR piece of the puzzle that I think you’re smart enough to figure out.

So, take a look at the picture below, and imagine what’ll happen if you take both lats and shorten them at the same time.

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It’ll produce something like this:

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Notice how the back of the body is being closed off and the front of the body appears to be opening…this is called bilateral extension. It creates a position where your ribs pop up and out in the front, and your pelvis rolls forward into anterior tilt (a good visual for a pelvis rolling forward is to think of dumping water out of the front of a bucket).

This, my friend, is why the lats are like Bane: when unopposed they have the ability to completely dominate and wreak havoc upon your system.

*Remember, your goal is ribs down and hips underneath…this is doing the opposite

Rectus Femoris and TFL (aka The Joker)

Rectus-femoris
Rectus-femoris
tfl.jpg

The Joker represents another arch nemesis that Batman must face routinely to bring balance and peace to Gotham. The Joker, however, is not easily defeated. He is cunning, creative, and always finds ways to disturb the peace…much like your rectus femoris and TFL.

Of particular interest is their ability to pull either innominate into anterior tilt. You can visualize this by thinking of either muscle like a string that’s attached to the front of the pelvis that you’re pulling down on.

Similar to the lats, this is pulling the pelvis into a position we don’t want.

Serratus Anterior (aka Robin)

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When Batman is in trouble he can often rely on Robin to provide some much needed help and assistance.  Luckily for you, you have a serratus anterior to help your big guns above (obliques and transverse abdominis) get your ribs into a better position by pulling the ribs "back and down."

To help visualize this take a look at the picture above, and imagine what happens if you shorten that muscle in both directions.  The scapula is being pulled towards the ribs, but the ribs are also being pulled back towards the scapula.  Thus, if you see someone with a prominent rib flare, you should probably start thinking about how you can put Robin in a position to help Batman, but that's what we'll be talking about in Part II so let's not get ahead of ourselves.

Closing Thoughts

While your head may be spinning from the anatomy, I'd like to ask you to sit on it for a few days and think about the relationship between all of those muscles.

Go back through the pictures and try to visualize what happens when a particular muscle shortens/contracts.  What's happening to the pelvis?  What's happening to the ribs?

As soon as your comfortable doing that, try taking it a step further by thinking your way through how they impact each other (the video at the beginning of the post can help with this as well).

Understanding these relationships will go a long way in helping you transition nicely to Part II of our discussion next week.

I also think it's important to go ahead and address the fact that in this series we're going to be looking at one small piece of a very large puzzle.  And in order to do that I'm going to have to make some generalizations, and I'm going to have to talk about things in isolation that are truly meant to be looked at as a whole.  For example, nowhere in this two part series am I going to be talking about hamstrings, but when you look at the big picture hamstrings are really, really important.  And the same thing can be said for just about any muscle because the human body is such a beautiful, connected and complex system.

Now, I'm not saying that the information being presented to you is worthless because it isn't.  I wouldn't have taken the time to write it if I thought it was.  I'm merely telling you this so that you don't lose site of the forest while we take some time to focus on a few individual trees.

Always think big picture, and always think about how everything connects.

The core is important, but like I said:  it's only one small piece of a very big puzzle.

about the author

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James Cerbie is just a life long athlete and meathead coming to terms with the fact that he’s also an enormous nerd.  Be sure to follow him on Twitterand Instagram for the latest happenings.

[i] Sahrmann, Shirley. “Abdominal Muscles.” Diagnosis and Treatment of Movement Impairment Syndromes. St. Louis: Mosby, 2002. 69.